1. Field of the Invention
The present invention relates to a shaft for golf clubs.
2. Description of the Related Art
A so-called carbon shaft has been known as a shaft for golf clubs. A sheetwinding method has been known as a method for manufacturing the carbon shaft.
A prepreg includes a matrix resin and a fiber. Many types of prepregs exist. A plurality of prepregs having different resin contents have been known. In the present application, the prepreg is also referred to as a prepreg sheet or a sheet.
In the sheetwinding method, the type of a sheet, the disposal of the sheet, and the orientation of a fiber can be selected. A laminated constitution is designed corresponding to desired characteristics of a shaft.
Japanese Patent Application Laid-Open No. 2002-282398 discloses a tubular body in which a 0°-compression strength σ and in-plane shear strength SI of a bias layer, and a tensile elastic modulus E of a reinforcing fiber in the bias layer satisfy three predetermined formulae.
Japanese Patent Application Laid-Open No. 2003-103519 discloses a prepreg sheet in which a tensile elastic modulus E of a reinforcing fiber and a 6°-compression strength σ of a fiber reinforced composite material satisfy two predetermined formulae. The gazette discloses that the prepreg sheet is used for a bias layer.